BONES OF THE SKULL. 757 



from the os frontis, the sphenoid, the lacrymal, and the malar bone ; 

 the ethmoid and the palatine rarely entering into its composition. 



(2160.) The os eihmoides, the vomer, and the turbinated bones will 

 be described minutely when we speak of the olfactory apparatus, which 

 they contribute to form. 



(2161.) The inferior maxilla in Mammals is characterized by two 

 circumstances, which distinguish it from that of other Vertebrata. It 

 consists, in the first place, of only two lateral pieces, exactly similar to 

 each other, joined together at the chin by a symphysis in many orders ; 

 but in others even this symphysis is obliterated at an early age, and 

 in the adult the two lateral halves would seem to form but one piece. 



(2162.) Another character peculiar to the lower jaw of a Mammal is, 

 that it is moveably articulated with the temporal bone by means of a 

 convex and undivided condyle. 



(2163.) These marks, identifying the mammiferous lower jaw, ought 

 to be well remembered by the palaeontologist. 



(2164.) We shall hereafter have occasion to describe the teeth that 

 arm the jaws of the different tribes of quadrupeds; and therefore we 

 now proceed to examine their cranial cavity, and the bones that enter 

 into its formation. 



(2165.) The frontal bones (figs. 380, 381, 1, l) are generally two in 

 number ; and even when, as in Man, they seem to form but one bone, 

 the two lateral halves are produced from separate points of ossification, 

 and only coalesce as age advances : sometimes, indeed, even in the adult, 

 they remain permanently separated by suture. 



Fig. 381. 



Section of the skull of the Pig. 



(2166.) The parietal bones (figs. 380, 381, 7, 7) occupy their usual 

 position; and although generally double, as in the human skeleton, 

 they are not unfrequently consolidated together, even at an early age, so 

 as to represent but a single bone. 



(2167.) The occipital bone consists primarily of the same pieces as 



